packages in the capitol. federal authorities say letters sent topresidentobamatested positive for the toxic substance ricin. here is jay corny today. >> there was a letter sent to, addressed to the president at an off-site mail facility it was noticed to contain a suspicious substance, and tests were undertaken. >> michael: thankfully it was intercepted before it reached the white house. since 9/11 all white house and congressional mail is sorted at a separation lobingation. this morning two floors evacuated when a letter was discovered there. in the hallway outside of senator richard shelby's office was cleared after reports that he also received a suspicious package. in phoenix there was report of a suspicious package at john mccain's office. and karl levin's office was evacuated because of similar circumstances. a man has been arrested with a backpack full of letters, and he is in custody. coming up rt rybak will give us his take on the votings, plus at least progressives have mark sanford to keep their sparts up. and later, scrutinized and also misunde

department has still not named any suspects in the bombing but this morningpresidentobamacalledit an act of terrorism. >> obama: this was a heinous and cowardly act. given what we now know took place, the fbi is investigating it as an act of terrorist. any time bombs are used to bomb civilians it is an act of terror. what we don't yet know, however is who carried out this attack or why. >> michael: the president will visit boston on thursday and today investigators combed through the remains crawling on sidewalks, scraping up fragments, and looking for any signs of who did this and why they did it. those tiny remnants helped the fbi solve other bombings like the 1993 attack on the world trade center. just a small fragment of the van that carried the explosives was found in the rubble, and that helped investigators identify the bomber. boston authorities say the bombs were made from pressure cookers and they believe a nylon backpack was holding the device. patients came in with wounds from small pellets and sharp nail-like objects. they're saving all of those pieces as evidence. they hop